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#ifndef IMAGE_TRANSPORT__CAMERA_SUBSCRIBER_HPP_
#define IMAGE_TRANSPORT__CAMERA_SUBSCRIBER_HPP_

#include <functional>
#include <memory>
#include <string>

#include "rclcpp/node.hpp"

#include "sensor_msgs/msg/camera_info.hpp"
#include "sensor_msgs/msg/image.hpp"

#include "image_transport/visibility_control.hpp"

namespace image_transport
{

class ImageTransport;

/**
 * \brief Manages a subscription callback on synchronized Image and CameraInfo topics.
 *
 * CameraSubscriber is the client-side counterpart to CameraPublisher, and assumes the
 * same topic naming convention. The callback is of type:
\verbatim
void callback(const sensor_msgs::msg::Image::ConstSharedPtr&, const sensor_msgs::msg::CameraInfo::ConstSharedPtr&);
\endverbatim
 *
 * A CameraSubscriber should always be created through a call to
 * ImageTransport::subscribeCamera(), or copied from one that was.
 * Once all copies of a specific CameraSubscriber go out of scope, the subscription callback
 * associated with that handle will stop being called. Once all CameraSubscriber for a given
 * topic go out of scope the topic will be unsubscribed.
 */
class CameraSubscriber
{
public:
  typedef std::function<void (const sensor_msgs::msg::Image::ConstSharedPtr &,
      const sensor_msgs::msg::CameraInfo::ConstSharedPtr &)> Callback;

  IMAGE_TRANSPORT_PUBLIC
  CameraSubscriber() = default;

  IMAGE_TRANSPORT_PUBLIC
  CameraSubscriber(
    rclcpp::Node * node,
    const std::string & base_topic,
    const Callback & callback,
    const std::string & transport,
    rmw_qos_profile_t = rmw_qos_profile_default);

  /**
   * \brief Get the base topic (on which the raw image is published).
   */
  IMAGE_TRANSPORT_PUBLIC
  std::string getTopic() const;

  /**
   * \brief Get the camera info topic.
   */
  IMAGE_TRANSPORT_PUBLIC
  std::string getInfoTopic() const;

  /**
   * \brief Returns the number of publishers this subscriber is connected to.
   */
  IMAGE_TRANSPORT_PUBLIC
  size_t getNumPublishers() const;

  /**
   * \brief Returns the name of the transport being used.
   */
  IMAGE_TRANSPORT_PUBLIC
  std::string getTransport() const;

  /**
   * \brief Unsubscribe the callback associated with this CameraSubscriber.
   */
  IMAGE_TRANSPORT_PUBLIC
  void shutdown();

  IMAGE_TRANSPORT_PUBLIC
  operator void *() const;

  IMAGE_TRANSPORT_PUBLIC
  bool operator<(const CameraSubscriber & rhs) const {return impl_ < rhs.impl_;}

  IMAGE_TRANSPORT_PUBLIC
  bool operator!=(const CameraSubscriber & rhs) const {return impl_ != rhs.impl_;}

  IMAGE_TRANSPORT_PUBLIC
  bool operator==(const CameraSubscriber & rhs) const {return impl_ == rhs.impl_;}

private:
  struct Impl;
  std::shared_ptr<Impl> impl_;
};

}  // namespace image_transport

#endif  // IMAGE_TRANSPORT__CAMERA_SUBSCRIBER_HPP_
